The present invention relates to tubular product containers and methods and apparatus for making containers and, more particularly, relates to tubular containers having a window for viewing the product contained therein.
Food and drink products and other perishable items are often packaged in tubular composite containers that are sealed at both ends. Conventional tubular composite containers typically include at least one structural body ply and are formed by wrapping a continuous strip of body ply material around a mandrel of a desired shape to create a tubular structure. The body ply strip may be spirally wound around the mandrel or passed through a series of forming elements so as to be wrapped in a convolute shape around the mandrel. At the downstream end of the mandrel, the tube is cut into discrete lengths and is then fitted with end caps to form the container.
To assist consumers in making purchasing decisions, it is desirable to provide a composite container for products constructed with one or more openings or windows in the container wall to enable the consumer to view the product stored therein. An opening or window into the container not only provides the consumer with the ability to compare the appearance of competing products, but also provides the consumer with confidence that the product does not have any defects, such as food spoilage in the case of food products, prior to making a purchase.
One example of a tubular container having a window for viewing the container contents from outside the container is disclosed in U.S. Pat. No. 1,894,295 to Scandore, which discloses a method of constructing a container having a window covered with a transparent material, such as cellophane. The container is constructed by spirally wrapping an inner ply of cardboard and cutting openings therethrough to provide sight openings. A transparent material, such as cellophane, is partially wound over or otherwise positioned on the exterior of the inner ply so as to cover the sight openings. An outer layer of cardboard having openings cut therein to coincide with the openings in the inner ply is then wrapped over both the inner ply and the transparent material in a direction opposite to the direction of wrap of the inner ply. A decorated outer wrapper having openings corresponding with the sight openings may be applied to the outer ply.
However, the composite container disclosed in the ""295 patent is not particularly suited for storing food products, especially those which have a liquid component. The transparent material does not provide an adequate moisture or gas barrier to seal the container and protect any stored food product from contamination or spoilage or to prevent wicking or leakage of the food product into and through the container wall. More generally, aligning the sight openings cut in the consecutive plies of material when wrapping the plies around the mandrel to form a container also creates many manufacturing difficulties, especially where the constituent plies of material are wrapped at relatively high speeds, for example 400 feet per minute. Variations in ply speed and splices in the ply material can cause misalignment of the sight openings, resulting in excessive material waste due to the discarding of defective containers.
Typically, tubular composite containers for storing food products include a liner ply on the inner surface of the paperboard body ply. The liner ply prevents liquids such as juice from leaking out of the container and also prevents liquids from entering the container and possibly contaminating the food product stored therein. Preferably, the liner ply is also resistant to the passage of gasses, so as to prevent odors of the food product in the container from escaping and to prevent atmospheric air from entering the container and spoiling the food product. Thus, the liner ply provides barrier properties and the body ply provides structural properties. Conventional liner plies most often include aluminum foil, which has good barrier properties and also has advantageous strength properties. In particular, the liner is wound onto the mandrel prior to the winding of the body ply and must be sufficiently strong and stiff to be independently wound on the mandrel without stretching or wrinkling. Because of the support provided by the foil layer of the liner, such liners are known as xe2x80x9csupportedxe2x80x9d liners. One or more polymeric layers are normally adhered to the foil to further improve the barrier properties of the liner and it is sometimes the case that the foil layer is not necessary for barrier properties, but is included in the liner only to provide support.
However, foils are nontransparent and thus, are not suitable for covering a sight opening through the container wall. It is therefore desired to provide a container and a method of making such a container that includes a liner of sufficiently low opacity to allow viewing of the stored product from outside the container, but that provides both moisture and gas barriers to prevent contamination and spoilage of stored food product and to prevent wicking and leakage of the food product into and through the container wall. Because such a liner would necessarily not include a foil layer, the liner would be an xe2x80x9cunsupportedxe2x80x9d liner.
The use of unsupported liners presents many technical challenges. For example, because of the problems associated with winding an unsupported liner on the mandrel, such as stretching, creasing or other misshaping of the liner, it has not been commercially feasible with conventional winding apparatus and methods to manufacture a container having an unsupported liner ply. The assignee of the present application and others in the field have striven toward developing practicable methods and apparatus for making containers with such unsupported film liners. For example, the assignee of the present application has developed methods and apparatus for making composite containers with unsupported liners made of polymer film, as disclosed in commonly owned U.S. Pat. No. 5,846,619 entitled xe2x80x9cPolymeric Liner Ply for Tubular Containers and Methods and Apparatus for Manufacturing Samexe2x80x9d issued Dec. 8, 1998, and U.S. Pat. No. 5,829,669 entitled xe2x80x9cTubular Container and Methods and Apparatus for Manufacturing Samexe2x80x9d issued Nov. 3, 1998, the entire disclosures of which are hereby incorporated herein by reference.
In light of the foregoing, there is need for an improved container and method of making the same having a window through the container wall. Such a container should include a liner providing both a moisture and optionally a gas barrier to prevent contamination and spoilage of stored food product and to prevent wicking and leakage of the food product into and through the container wall and at the same time allow viewing of the product. In addition, the improved container must be capable of being manufactured efficiently and inexpensively, and in particular, be capable of being efficiently constructed by wrapping the constituent plies at relatively high speeds while maintaining accurate alignment of the sight openings provided in the material plies.
The present invention provides a multi-ply tubular container having a window for viewing the product contained therein. The window is advantageously formed in a paperboard body ply and covered by a transparent polymeric liner ply on the inner surface thereof. In this manner, the product can be viewed through the window and is also sealed from leaking out of the container. More particular, the container is constructed of at least one body ply formed of a fibrous paperboard. The body ply is wrapped into a tubular shape having an inner surface and an outer surface. The body ply defines at least one aperture therethrough such that when the body ply is wrapped into a tubular shape the aperture forms a window into the container. The liner ply is adhered to the inner surface of the body ply such that a portion of the liner ply extends across the aperture in the body ply. The liner ply can be adhered to the inner surface of the body ply with a wet adhesive or a polymeric adhesive. The tubular container may further include a label ply adhered to the outer surface of the body ply and defining at least one aperture therethrough corresponding to the aperture in the body ply. The body ply and liner ply can be either helically or longitudinally wound.
Advantageously, the liner ply can be a polymeric material having a low opacity that allows the product in the container to be viewed through the window. In one embodiment, the liner ply can be substantially transparent. The liner ply may include a polymeric moisture barrier layer, such as a polyolefin polymer. In other embodiments, the moisture barrier layer may include at least one of the group of polyester, nylon, ethylene vinyl alcohol copolymer and blends thereof. In a preferred embodiment, the liner ply has a thickness of less than about three mils.
The present invention also provides an associated method of manufacturing multi-ply tubular containers having a window for viewing the product contained therein. The method includes the steps of advancing a continuous polymeric liner ply towards and wrapping the liner ply around a shaping mandrel to create a tubular shape. Advantageously, the liner ply is comprised of a polymeric material having a low opacity such that the product in the container can be viewed through the liner ply. A continuous body ply formed of paperboard is also advanced towards the mandrel. Apertures are cut in the body ply at predetermined intervals along its length. The body ply is wrapped around the previously wrapped liner ply on the mandrel so that the liner ply becomes adhered to the body ply to create a tubular shape having a viewing window sealed by the liner ply. Once constructed, the tubular shape is cut into discrete lengths adjacent the end of the mandrel. At least one end of each tube length can then be rolled outwardly to form a bead or flange for metal end. Preferably, the liner ply is elastically deformable to prevent the bead from unrolling.
In another embodiment, a continuous polymeric liner ply is advanced towards and wrapped around a shaping mandrel to create a tubular shape. The liner ply is preferably comprised of a polymeric material having a low opacity such that the product in the container can be viewed through the liner ply. A body ply and a label ply are advanced towards the shaping mandrel. Apertures are cut through the label ply at predetermined intervals along the length of the label ply. The location of the apertures in the label ply are registered. Apertures are cut through the body ply at predetermined intervals along the length of the body ply corresponding to the apertures cut in the label ply. The body ply is wrapped around the previously wrapped liner ply on the mandrel. The label ply is wrapped around the previously wrapped body ply and liner ply so that the apertures in the label ply are aligned with apertures in the body ply to create a tubular shape having a viewing window through both the label and body plies.
Accordingly, there has been provided a tubular container having a window through the container wall sealed by a transparent polymeric liner ply for viewing the product stored therein from outside the container. Advantageously, the liner provides a moisture and gas barrier to protect any stored food product from contamination and spoilage and to prevent wicking and leakage of the food product into and through the container wall. There has also been provided an associated method of efficiently and inexpensively manufacturing a tubular container having a window through the container wall for viewing the product stored therein; the container being efficiently constructed by wrapping the constituent plies at relatively high speeds while maintaining accurate alignment of the sight openings provided in the plies of material.